package org.apache.solr.search.function.distance;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.spatial.DistanceUtils;
import org.apache.solr.search.function.DocValues;
import org.apache.solr.search.function.MultiValueSource;

/**
 * While not strictly a distance, the Sq. Euclidean Distance is often all that
 * is needed in many applications that require a distance, thus saving a sq. rt.
 * calculation
 */
public class SquaredEuclideanFunction extends VectorDistanceFunction {
	protected String name = "sqedist";

	public SquaredEuclideanFunction(MultiValueSource source1,
			MultiValueSource source2) {
		super(-1, source1, source2);// overriding distance, so power doesn't
									// matter here
	}

	@Override
	protected String name() {

		return name;
	}

	/**
	 * @param doc
	 *            The doc to score
	 */
	@Override
	protected double distance(int doc, DocValues dv1, DocValues dv2) {

		double[] vals1 = new double[source1.dimension()];
		double[] vals2 = new double[source1.dimension()];
		dv1.doubleVal(doc, vals1);
		dv2.doubleVal(doc, vals2);

		return DistanceUtils.squaredEuclideanDistance(vals1, vals2);
	}

	@Override
	public boolean equals(Object o) {
		if (this == o)
			return true;
		if (!(o instanceof SquaredEuclideanFunction))
			return false;
		if (!super.equals(o))
			return false;

		SquaredEuclideanFunction that = (SquaredEuclideanFunction) o;

		if (!name.equals(that.name))
			return false;

		return true;
	}

	@Override
	public int hashCode() {
		int result = super.hashCode();
		result = 31 * result + name.hashCode();
		return result;
	}
}
